A series of synthetic iron porphyrins are being prepared for the purpose of modelling the oxygen binding hemoproteins--hemoglobin, myoglobin, and cytochrome P-450. The structures of these synthetic models are being determined by X-ray diffraction and their physical properties (Mossbauer, electronic, and MCD spectra, magnetic moments, and vibrational spectra) are being determined for comparison with the natural hemoproteins. Special emphasis is being given to studies of models for the hydroxylase cytochrome P-450. Synthetic models for the low-spin and high-spin ferric and the ferrous carbonyl stages of P-450 have been characterized. Preparation and structural characterization of synthetic analogues of the deoxy ferrous form are progressing. Ruthenium analogues of these iron porphyrins are being prepared, including a dioxygen complex. A new "capped" porphyrin and an extensive series of binary "face-to-face" porphyrins have been prepared.